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Start slow, I would save the cardinals for last, they are the most sensitive. This also keeps stocking lower for a while while you get used to managing the system. Keep a good water change schedule, at least weekly. It usually works best to pick one day and stick with it (something like every Sunday you are going to do a water change). Think of it like what it is, a system. Not like a glass bax that your fish live inside of, but a whole system that needs to be balanced and will change over time.

Any tank should get weekly water changes. This is the best way to keep water quality as high as possible. This means fish are healthier, they grow better, etc. It also means that when life happens and you miss one (or more) there is more room for error.

High quality food and water will allow you to prevent most health problems. When you have any issues at all do a water change. This means algae, stressed fish, a fish death, anything bad is treated with water changes (except the rare case where water changes are causing the problem, even then it is usually how they are done, not water changes in general).

I would do at least 25%. My tanks get 80% or so, but DO NOT do this, especially not right away. If done right there are no issues, but the larger the water change the more severe any problems are. So if you do 20% and the temp is a little off no big deal, 80% and all the fish could have problems.

When in doubt about temp go slightly cooler rather than slightly warmer. This is more natural for them (rain cools water) and can even trigger breeding.

I am on well water so no dechlorinator for me.

You are on the border line, but I think a water change system that hooks up to the sink is a better option for you than using buckets. Drain the tank, vacuum the gravel (or any debris on top of sand if you use sand), stop the water, add dechlorinator to the tank (when in doubt add a little extra), and fill.

Start with 10-20% and if you want or need to go larger do so at small steps, 5% more each time. Don't just jump into larger water changes.